Cardiac output (CO) is the fundamental performance measure of the heart. Recent advances have permitted automatic thermodilution measurement of CO with updates every 1-5 minutes, but these updates are heavily weighted by prior data and thus distort, delay and attenuate the signal which derives from sudden changes in flow. A thermal noise reduction technique has been developed which allows the measurement of CO with independent updates more frequent than once a minute and permits monitoring of CO during changes in baseline blood temperature which are consequences of interventions. Phase I in vitro and in vivo studies have shown that this method is more accurate, more precise (2-fold), and bas greater measurement speed (>7 times) than the Baxter Vigilance CCO instrument. In Phase ll, we will develop a process appropriate to manufacture catheters in production volumes. A stand-alone clinical microprocessor controlled CCO instrument will also be developed, as will the necessary software and algorithms for the collection, analysis and data display. The entire system will be extensively tested in a series of porcine experiments for accuracy, update speed and the ability to measure flow under conditions of significant thermal noise. The ability of the TTI CCO to provide frequent measurements, independent of prior data, will be of great benefit in the management of unstable patients with variable cardiovascular hemodynamics. PROPOSED COMMERCIAL APPLICATION: It is anticipated that many of the TDCO catheters sold world-wide (>2 million annually) will eventually be replaced by CCO catheters. The rapid and independent measurements as well as the thermal noise rejection provided by the TTI CCO method is expected to increase the acceptance of CCO and open up other applications and markets unreachable by the currently available techniques. The added benefit of continuous cardiac output, is expected to justify the modest added cost of the CCO device over traditional TDCO.